Comsonics, Inc.

Richard L Shimp

Dennis A Zimmerman

John J Murphy

Marc-Yvon Comeau

A small, portable signal generator provides a unique marker signal modulated with a selectable number of degrees of freedom for insertion into a portion of a broadband communication system (BCS) such as a subscriber installation site that may or may not be connected to the remainder of the BCS. If payload signals are not present or brief interference with payload signals is tolerable, a high level marker signal may be injected with level control upon detection of an egress signal to detect very minor leakage sources and thus increase quality of the qualification of installation or repairs. If payload signals are present, marker signals are held to non-interfering levels and frequencies. Authentication of a signal received through an antenna is expedited and increased in confidence level by synchronization of the marker signal modulation pattern and the signal detector in a receiver.

Miniature mobile marker system and method

Detecting ingress of a transmitted signal into a cable communication system due to a radio frequency signal transmitted from a moving vehicle and interrogation of transmitter location over a separate wireless link provides monitoring of shielding integrity or flaws there in a cable communication system. The location of a shielding flaw may then be precisely located in a closed loop fashion without risking overload of the cable communication system or interference with upstream signaling therein by detecting ingress signal strength and controlling transmitted signal strength while providing a user-perceptible indication of ingress signal strength which is compensated for the control of transmitted signal strength and thus indicates proximity of a hand-held instrument or transmitter to said shielding flaw.

Communication system fault location using signal ingress detection

A segmented upstream management system for a bidirectional coaxial network of the type including a bidirectional trunk (14) having a plurality of bidirectional feeders (12) and a plurality of drops (10) is disclosed. The management system includes a number of rerouting devices (36) connected in the bidirectional trunk at intervals so as to divide the number of drops into predefined groups. A plurality of upconverters (40) are connected to the outputs of the rerouting devices. The upconverters are in turn connected to a return only trunk (38) which transmits the frequency diverse, upconverted signals and each respective local oscillator signal from the upconverters to a hub or headend site (16). At the headend site, the return only trunk is connected to a plurality of synchronous down converters (42) which produce down converted signals from each of the predefined groups. FSK and other frequency/phase dependent data retain coherence by phase locking each down converter to the actual local oscillator which provided each respective upconversion. The system has particular application to bidirectional CATV systems which carry digital data transmissions from subscriber drops to a central hub or headend site.

Segmented upstream management for cable television

A status monitor for coaxial cable networks is disclosed. The monitor is designed to be directly attached to an output port of an amplifier/repeater in the network and is used as an aid in trouble shooting faults in the network. The monitor comprises a detector (12 or 40) which generates a d.c. voltage indicative of the level of a pilot frequency signal on the network. This d.c. voltage is supplied to a plurality of voltage comparators (18, 20 and 22) which compare the d.c. voltage with different reference voltages in order to sense different fault conditions. If a fault condition is sensed, the outputs of the comparators are used by a tone selection logic (24) and an OR logic switch (26) to control a voltage controlled oscillator (28) to generate a modulating tone. A signal from a crystal controlled oscillator (32) or an IF output of the detector (40) is modulated by the tone produced by the voltage controlled oscillator and radiated. This tone modulated radiated signal may then be used by a technician in the field to detect both the location and the nature of the sensed fault in the network.

Status monitor

A split-band, redundant amplifier system is disclosed. The system has at least two identical amplifiers (1, 2) each capable of amplifying signals having frequencies within a predetermined pass band. A first filter (3) divides signals into at least two contiguous split-bands within the pass band. A second filter (5) combines the signals in the split-bands. In normal operation, the amplifiers are connected in parallel between the two filters, and each amplifier amplifies signals in only one of the split-bands. Switches (SW1, SW2, SW3, SW4, SW5, SW6, SW7, and SW8) are connected to the amplifiers and the filters and are operative to selectively connect an input signal to the first filter or to one of the amplifiers and to selectively connect the output of the second filter or the output of one of the amplifiers to the output of the system. A sensing circuit (7) is connected to the outputs of each of the amplifiers and detects when an amplifier becomes inoperative. When an amplifier becomes inoperative, the sensing circuit disconnects the inoperative amplifier from the first and second filters and connects an operative amplifier to the input and output of the amplifier system.

Split-band redundant amplifier system

A method and apparatus of compatibly and simultaneously transmitting and receiving an encoded signal with the normal visual and aural carrier of a television signal is disclosed. The encoded signal is used as a modulating signal to frequency modulate the visual carrier frequency signal prior to amplitude modulating the visual carrier frequency signal with a source of composite video signals. Normally, the introduction of additional sideband power even in the form of constant amplitude components will cause visual distortion to a received picture due to the normal Nyquist shaped bandpass characteristics of the intermediate frequency amplifier in the television receiver. This distortion is reduced or eliminated in several ways. The maximum allowable frequency modulation deviation can be limited so that the visual distortion is substantially reduced. Where greater frequency modulation deviation is required, the interfering beats which appear as horizontal lines are made less visable by adjusting the frequency modulation deviation so that these lines roll vertically at a maximum rate. A more desirable approach is to amplitude predistort the frequency modulated visual carrier frequency signal in a complimentary mode to the slope of the video intermediate frequency amplifier circuits of the television receiver. In this manner, an incidental amplitude modulation would be added to the television visual carrier at the transmitter, and this incidental amplitude modulation is in the opposite polarity of the slope of the modulation taking place in the receiver. In other words, by predistorting the frequency modulated visual carrier frequency signal, the signal is in effect pre-equalized to the Nyquist bandpass characteristics of the television receiver intermediate frequency amplifier. The predistortion of the frequency modulated visual carrier signal may be accomplished passively with a bandpass filter having its lower frequency slope at the television picture carrier frequency and having bandpass response characteristics which are complimentary to the Nyquist bandpass characteristics of the television receiver intermediate frequency amplifier. Instead of a passive bandpass filter, similar results are obtained by active, pre-equalizing circuits in the transmitter. Specifically, a phase opposite correction signal derived from the encoded signal is added to the composite video signal prior to amplitude modulating the frequency modulated visual carrier frequency signal. In any case, normal aural carrier generation methods avoid any interference by the addition of a frequency deviation of the visual carrier. The received signal is detected to separately reproduce the encoded signal.

Compatible transmission of an encoded signal with a television

The detector is primarily useful in detecting RF leaks due to defects in the shielding in a CATV coaxial cable distribution network. RF leaks are detected by transmitting a unique signal and using a very narrow band receiver to detect the unique signal to thereby detect small amounts of RF leakage from the CATV coaxial cable distribution network at the locations of defects in the shielding. The leakage from the CATV coaxial cable distribution network is due to defects in the shielding such as small cracks in the cable, loose fittings or other non-RF tight conditions. The detector is a three-part system including a transmitter, a remote cable powered preamp and antenna assembly, and a narrow band receiver providing an audio output. The transmitter is designed to be permanently installed at the head end location and is modulated with a unique audio tone. An RF leak is detected by moving the remote preamp and antenna assembly along the coaxial cable distribution network of the CATV system. When the remote preamp and antenna assembly picks up leakage RF energy, the unique audio tone will be detected, and the detected audio signal fed to a loud speaker or earphones. The audio tone is readily recognized by the operator.

Growing community of inventors

Harrisonburg, VA, United States of America

Richard L Shimp